Lubrication properties of trimethylolpropane esters based on palm oil and palm kernel oils

Due to the global drive towards biodegradable products, trimethylolpropane [2‐ethyl‐2‐(hydroxymethyl)‐1, 3‐propanediol] (TMP) esters based on palm and palm kernel oils were synthesized, their lubrication properties evaluated, and their potential as base stock for biodegradable lubricants assessed. Two types of TMP esters were considered: palm kernel (PKOTE) and palm oil (PPOTE) TMP esters, derived from palm oil and palm kernel methyl esters, respectively. Lubrication properties such as viscosity, viscosity index (VI) and pour point (PP) were determined according to methods of the American Society for Testing and Materials. Wear and friction properties were evaluated using a four‐ball test machine, while oxidative stability was studied with the Penn State Micro‐oxidation thin‐film test. High VI ranges between 170 to 200 were recorded for these base stocks. PP were relatively high, between 4 to —1 °C, but were improved to at least —33 °C in high oleic palm oil TMP esters. The effects of chemical structure and impurities on wear properties and oxidative stability were also studied. The presence of methyl esters was found to improve wear, but hydroxyl groups in mono‐ and diesters had negative effects at high concentrations. Differences in chemical structures of PKOTE and PPOTE were shown to affect friction and wear results. Both base fluids exhibit oxidative stability comparable to other high oleic base fluids.     

植物油基润滑油应用研究现状

植物油具有生物可降解性、低挥发性、优良的润滑性和良好的黏温性,但植物油存在热氧化安定性差、低温性能差等缺陷,不能直接作润滑油和润滑添加剂应用,需要对其进行改性。常用化学改性方法有选择性氢化、酯交换和环氧化等,其中环氧化-开环反应引入活性基团和双键上的自由基加成反应是合成植物基润滑油添加剂的两种有效的改性方法。最后,就改性植物油用作可降解润滑油基础油和添加剂提出了研究方向并做了展望。     

Development of Fully Bio‐Based Lubricants from Agro‐Industrial Residues under Environmentally Friendly Processes

Biolubricants are becoming interesting alternatives to mineral lubricants. Despite their advantages, development of lubricants from vegetable oils may compete with food production, turning their use impractical due to socio‐economic aspects. Here, cardanol is used as raw material in the synthesis of novel biolubricants under environmentally friendly conditions. These compounds are characterized by NMR and Fourier transform infrared spectroscopy. Thermal‐oxidative studies show the elevated stability and higher onset oxidative temperatures. Tribological analyses performed under high‐frequency linear‐oscillation motion indicate lower coefficients of friction and wear rates compared to a synthetic oil. Therefore, cardanol, under simple, fast, and sustainable processes can be transformed into valuable alternatives for petroleum‐based lubricants. Practical Applications: The novel cardanol‐based biolubricants presented in this work show interesting chemical and lubricity properties superior to standard synthetic oils, which make them potential substitutes for the current oil‐based products used as lubricants. Additionally, the ecofriendly methodologies employed reduce significantly the reaction time as well as eliminating the need for catalysts or solvents, making these processes viable alternatives for the traditional methods reported in literature for the synthesis of this class of compounds.     

Linseed and Complex Rosin Ester Oils Additivated with MWCNTs and Nanopearls for Gears/Wheel‐Rail Systems

An innovative biolubricant for gears/wheel‐rail systems is formulated; it is produced inexpensively using high‐viscosity vegetable oils modified with additives of unpurified carbon nanopearls (CNPs) and MWCNTs produced via carbon‐vapor deposition. Traditional lubricants made from non‐renewable sources can be replaced with such additive‐based oils. The addition of both unpurified carbon nanopearls and nanotubes containing nanoparticles of Fe, Ni, Co, or SiO₂ is a simple way to improve the tribological properties of biolubricants. Therefore, carbon nanostructures used as additives are not required to be purified or functionalized, thus reducing production costs. Tribological testing is performed with ball‐on‐disc, four‐ball, and twin‐disc machines for two high‐viscosity biolubricants. A complex rosin ester and linseed oil additivated with commercial and raw CNPs/MWCNTs are tested. Scanning electron microscope characterization is used to assess the morphology and structure of both the carbon nanopearls and the multiwalled carbon nanotube particles in addition to the worn metal surfaces. Additionally, X‐ray diffraction, FTIR spectroscopy, and inductively coupled plasma atomic emission spectroscopy are used to characterize the MWCNTs additives. Practical Applications: Biolubricant additivation with raw unpurified MWCNTs and CNPs for enhanced tribological performance. Presence of Fe, Ni, Co, and Si nanoparticles helps fine‐tune the friction coefficient and anti‐wear rates. The proposed method may prove useful in biolubricant formulation for applications in gears/wheel‐rail and metal machining systems.     

Frying performance of a sunflower/palm oil blend in comparison with pure palm oil

The aim of this study was to test the performance of a vegetable oil blend formulated as alternative to pure palm oil as frying medium. For this purpose, the evolution of many analytical parameters (free acidity, spectrophotometric indices, total polar components, fatty acid composition, short‐chain fatty acids, tocopherol and tocotrienol content and composition, color, flavor evaluated by means of an electronic nose) of the selected blend (sunflower/palm oil 65 : 35 vol/vol) has been monitored during a prolonged frying process (8 h discontinuous frying without oil replenishment) in comparison to pure palm oil. Sensory attributes of the fried food were also evaluated. The blend proved to keep qualitative parameters comparable to those shown by palm oil during the prolonged frying process. Even if some oxidation indices, such as spectrophotometric indices, short‐chain fatty acids and total polar components, increased faster in the blend, it showed a higher tocopherol content and a lower increment in free fatty acids as compared to pure palm oil. Chips fried in the two oils did not show significantly different sensory profiles.     

Thin-film test to investigate liquid oxypolymerization of nonvolatile analytes: Assessment of vegetable oils and biodegradable lubricants

A thin-film oxidation test was developed to investigate liquid oxypolymerization of nonvolatile analytes. Gel permeation chromatography (GPC) showed that the test delivered the required degree of oxidation with better than ±5% accuracy. The following oils were ranked according to their decreasing resistance to oxypolymer formation at 150°C: 90% oleic sunflower oil, triolein, meadowfoam oil, castor oil, canola oil, lesquerella oil, and soybean oil. Higher degrees of oxidation demonstrated the occurrence of oxidative gelation. Oxypolymerization tendencies of hydraulic fluids based on canola and rapeseed oils were comparable to those of canola oil without additives. The relative amount of C-C polyunsaturation present in the fatty acid chain was a major differentiating factor. However, oxidation inhibitors also reduced the rates of oxypolymerization, as demonstrated by sunflower oil-based hydraulic fluid. Canola and rapeseed lubricants needed better oxypolymerization control.     

Chemical modification of vegetable oils for lubricant applications

Owing to the unfavorable impact on the environment of mineral oil-based lubricants, there has been a steady increase in the demand for biodegradable, environment-friendly lubricants. However, development of a biodegradable base fluid that could replace or partially substitute conventional mineral oil is a big challenge. Vegetable oils are recognized as rapidly biodegradable and are thus promising candidates as base fluids in environment-friendly lubricants. Vegetble oils have excellent lubricity, but poor oxidation and low-temeprature stability. This paper presents a series of structural modifications of vegetable oils using anhydrides of different chain lengths. The reaction was monitored and products were confirmed by NMR, FTIR, gel permeation chromatography, and thermogravimetric analysis (TGA). Experimental conditions were optimized for research quantity and for laboratory scale-up (up to 4 lb=1.8 kg). The thermo-oxidation stability of these new lubricant base fluids was tested using pressure differential scanning calorimetry and TGA. The chemically modified base fluids exhibit superior oxidation stability in comparison with unmodified vegetable oils. These base fluids in combination with suitable additives exhibit equivalent oxidation stability compared with mineral oil-based formulations.     

Correlation between physicochemical analysis and radical‐scavenging activity of vegetable oil blends as affected by frying of French fries

The main goal of the present work was to compare and correlate the results of physicochemical parameters and antiradical performance of some oil blends during deep‐frying, which will be an initial indicator for applying antiradical tests for monitoring deep‐frying oils. Two oil blends were prepared. The first blend was a mixture (1 : 1, wt/wt) of sunflower seed oil and palm olein (SO/PO) and the second was a mixture (1 : 1, wt/wt) of cottonseed oil and palm olein (CO/PO). The oil blends were evaluated during intermittent frying of French fries on two consecutive days for 16 h, with oil replenishing after 8 h. Changes in the fatty acid profile and some physicochemical parameters (peroxide value, color index, viscosity, total polar compounds and UV absorbance at 232 and 270 nm) were used to evaluate the alterations during frying. A quick spectrophotometric method was developed to assess deep‐frying oil quality. With the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) method, the neutralization of the stable radical DPPH by antioxidants present in the oil during frying was measured. Radical‐scavenging activity (RSA) of both oil blends was recorded during frying, wherein the results showed that the SO/PO blend had the highest RSA. It was evident from the results that a proportional correlation and positive relationship existed between the levels of fatty acids and the physicochemical characteristics of the vegetable oil blends and their RSA. The initial results obtained allow us to suggest that antiradical measurements could be used to quantify the oxidative and hydrolytic deterioration of vegetable oils upon frying.     

Influence of Different Moisture Contents on the Stability of Tocochromanols in Bulk Oils at 25 °C Storage

The stabilities of tocochromanols including α‐tocopherol, α‐tocotrienol, γ‐tocopherol, γ‐tocotrienol, and δ‐tocotrienol in grape seed oil, palm oil, or stripped soybean oil with added tocotrienol mixtures (SOTT) were determined under relative humidity (RH) 0, 32, 75, and 93% at 25 °C for 8 months of storage. Stability of tocochromanols was significantly influenced by the presence of moisture and other tocochromanols. Tocochromanol stability in grape seed oil was high at RH 75%, whereas palm oil had significantly lower tocochromanol content at RH 75% compared to those under other RH (p < 0.05). Tocochromanol stability in SOTT was high at RH 0%. δ‐Tocotrienol had the highest stability followed by α‐tocotrienol, γ‐tocotrienol, and α‐tocopherol in SOTT. Moisture content in palm oil was the lowest while that in SOTT was the highest at the same RH. Oxidative stability of palm oil was the highest followed by grape seed oil and SOTT based on conjugated dienoic acid content and p‐anisidine values. Moisture in oils affects the stability of tocochromanols and oxidative stability in vegetable oils.     

Evaluation of partially hydrogenated methyl esters of soybean oil as biodiesel

Biodiesel, an alternative fuel derived from vegetable oils or animal fats, continues to undergo rapid worldwide growth. Specifications mandating biodiesel quality, most notably in Europe (EN 14214) and the USA (ASTM D6751), have emerged that limit feedstock choice in the production of biodiesel fuel. For instance, EN 14214 contains a specification for iodine value (IV; 120 g I₂/100 g maximum) that eliminates soybean oil as a potential feedstock, as it generally has an IV >120. Therefore, partially hydrogenated soybean oil methyl esters (PHSME; IV = 116) were evaluated as biodiesel by measuring a number of fuel properties, such as oxidative stability, low‐temperature performance, lubricity, kinematic viscosity, and specific gravity. Compared to soybean oil methyl esters (SME), PHSME were found to have superior oxidative stability, similar specific gravity, but inferior low‐temperature performance, kinematic viscosity, and lubricity. The kinematic viscosity and lubricity of PHSME, however, were within the prescribed US and European limits. There is no universal value for low‐temperature performance in biodiesel specifications, but PHSME have superior cold flow behavior when compared to other alternative feedstock fuels, such as palm oil, tallow and grease methyl esters. The production of PHSME from refined soybean oil would increase biodiesel production costs by US$ 0.04/L (US$ 0.15/gal) in comparison to SME. In summary, PHSME are within both the European and American standards for all properties measured in this study and deserve consideration as a potential biodiesel fuel.     

Biolubricants: Raw materials,chemical modifications and environmental benefits

The depletion of the world's crude oil reserve, increasing crude oil prices, and issues related to conservation have brought about renewed interest in the use of bio‐based materials. Emphasis on the development of renewable, biodegradable, and environmentally friendly industrial fluids, such as lubricants, has resulted in the widespread use of natural oils and fats for non‐edible purposes. In this study, we have reviewed the available literature and recently published data related to bio‐based raw materials and the chemical modifications of raw materials. Additionally, we have analyzed the impacts and benefits of the use of bio‐based raw materials as functional fluids or biolubricants. The term biolubricants applies to all lubricants, which are both rapidly biodegradable and non‐toxic to humans and other living organisms, especially in aquatic environments. Biodegradability provides an indication of the persistence of the substance in the environment and is the yardstick for assessing the eco‐friendliness of substances. Scientists are discovering economical and safe ways to improve the properties of biolubricants, such as increasing their poor oxidative stability and decreasing high pour points. “Green” biolubricants must be used for all applications where there is an environmental risk.     

Motorenöle auf der Basis von Pflanzenölen – ein neuer Ansatz

Vegetable oil-based engine oils – A promising start These days most engine lubricants contain petrochemical base oils. A research project looked into the possibility of using vegetable oils and their derivatives (ester oils) for lubrication of four-stroke engines. The environmentally friendly, high-performance engine oils successfully tested in the first project were based on saturated esters and contained a zinc- and polymer-free additive package. Also realized was the second objective of a completely new lubrication concept which allows for the first time the use of unmodified rapeseed or sunflower oil for engine lubrication. The procedures mentioned here compensate for the basically poor ageing resistance of vegetable oils by a progressive renewal of the oil. The used oil is mixed with the fuel and burned without any detrimental effects on exhaust composition. Only low-ash and zinc-free additives were added to the vegetable oils. Initial and positive application know-how was gathered from a number of diesel engines using this combination of special oil and the novel lubrication concept. Environmentally friendly oils being constantly renewed in stationary engines are a promising start.     

Determination of the Oxidation Stability of Vegetable Based Lubricants

A modified Swift test was tested t o determine the oxidation stability of hydraulic fluids made of vegetable oils. At 110 °C an air current is passed through the oil to be tested. As a by-product of the oxidation, volatile acids are formed which are collected in water. They are determined conductometrically and registered automatically. Thus the method can be carried out without constant supervision. The neutralization figure, viscosity and conductivity showed a sudden rise at the same time. The test of different hydraulic oils led to stabilites between 1 and 30 hours. The comparison between the Baader test according to DIN 51554 and the modified Swift test showed similar results.     

Rapsölbasische Druckübertragungsmedien – Aufgaben,Anforderungen, Stand der Technik

Rapeseed Oil in Hydraulic Systems – Tasks, Requirements and Stand of the Art Rapeseed oil based hydraulic fluids have a lower level of ecotoxidity in comparison to the conventional petroleum-based lubricants and can be considered environmentally acceptable. Amongst the ecological point of view the acceptance of these fluids depends on several other aspects like economics and technology. In response to the growing interest in environmentally acceptable lubricants a hydraulic oil development program was initiated. Lubricant performance data, including laboratory evaluation and test experience, for a vegetable-based hydraulic fluid will be presented, identifying performance strengths and weaknesses.     

Some physical properties and oxidative stability of biodiesel produced from oil seed crops

Biodiesel is a cleaner burning fuel than petrodiesel and a suitable replacement in diesel engine. It is produced from renewable sources such as vegetable oils or animal fats. Biodiesel fuel was prepared from castor (CSO), palm kernel (PKO) and groundnut (GNO) oils through alkali transesterification reaction. The biodiesel produced was characterized as alternative diesel fuel. Fuel properties such as specific gravity, viscosity, calorific (combustion) value, The CSO, PKO and GNO were measured to evaluate the storage/oxidative stability of the oils to compare them with commercial petrodiesel. The biodiesel produced had good fuel properties with respect to ASTM D 6751 and EN 14214 specification standards, except that the kinematic viscosity of castor oil biodiesel was too low. The viscosity of castor oil biodiesel at different temperatures was in the range of 4.12–7.21 mm²/s. However, promising results which conformed to the above specification standards were realized when castor oil biodiesel was blended with commercial petrodiesel. At 28 °C the specific gravity recorded for CSO, PKO and GNO biodiesel was higher than the values obtained for petrodiesel. Commercial petrodiesel had the highest oxidative stability than biodiesel produced from CSO, PKO and GNO oils.     

Chemical synthesis of phytosterol esters of polyunsaturated fatty acids with ideal oxidative stability

In this study, direct esterification of phytosterols with polyunsaturated fatty acid (PUFA) catalyzed by sodium bisulfate to produce sterol esters of PUFA was performed without organic solvent. Considering on both degree of esterification (DE) and oxidative stability, response surface methodology (RSM) was employed for modeling the phytosterol esters of PUFA production to obtain a food grade process. The optimal and mild reaction conditions were obtained as follows: mass ratio of PUFA:phytosterols = 4:1; amount of catalyst: 3% of the raw materials weight; reaction temperature 130°C; reaction time 8 h. Under these conditions, the degree of esterification was up to 96%, GC, TLC, NMR and GC‐MS results showed that purity of purified sterol ester was above 99%, and β‐sitosterol linolenate account for about 88%. Sterol ester of PUFA possessed low peroxide value (PV) (0.96 meq/kg) and conjugated diene (CD) value (2.15 mmol/kg), and high oxidative induction period (OIP) (10.4 h). Addition amount of sterol ester of PUFA into soybean oil, rapeseed oil, and flaxseed oil below 1, 1, and 3%, respectively, could increase OIP of the vegetable oil. The primrose phytosterol esters of PUFA possessed very low melting point, crystallization temperature, and greater solubility in oils. All the characteristics favored the wide application of sterol ester of PUFA produced by the food grade process in different formulations of functional foods.     

The effect of natural and synthetic antioxidants on the oxidative stability of palm diesel

Crude and distilled palm oil methyl esters conveniently known as palm diesel have been successfully evaluated as diesel substitute. Crude palm oil methyl esters are produced from transesterification of crude palm oil with minor components such as carotenes and vitamin E still intact and they are reddish in colour. The distilled palm oil methyl esters are obtained after the recovery of minor components (e.g. Carotenes and vitamin E) From the crude palm oil methyl esters. These valuable minor components are preferably to be recovered as they can be sold as value-added products before they are burnt together with the methyl esters as fuel. Although both possesses fuel characteristics which are comparable to those of petroleum diesel, crude palm oil methyl esters are found to exhibit better oxidative stability (rancimat induction period >25 h) than distilled palm oil methyl esters (about 3.5 h). It is attributed to the presence of vitamin E (about 600 ppm), a natural antioxidant in the former. While the distilled palm oil methyl esters contain practically no vitamin E (<50 ppm) and as a result, they exhibit poor oxidative stability. Thus, the crude palm oil methyl esters meet the european standard for biodiesel (EN 14214) which has set a minimum rancimat induction period of 6 h. In the present study, research was conducted to enhance the oxidative stability of distilled palm oil methyl esters in order to meet the aforementioned standard. Natural and synthetic antioxidants were used in the present study to investigate their effect on the oxidative stability of distilled palm oil methyl esters. It was found that both types of antioxidant showed beneficial effects in inhibiting the oxidation of distilled palm oil methyl esters. Comparatively, the synthetic antioxidants were found to be more effective than the natural antioxidants as lower dosage (17 times less) was needed to achieve the minimum rancimat induction period of 6 h.     

Development of mineral oil free offset printing ink using vegetable oil esters

Until the middle of this century, fats and oils are the major raw material source for paints, coating and lubricating applications. These markets are completely taken over by petroleum based stocks due to their abundance and versatility. However, recent public awareness to use environmentally acceptable products that minimize pollution, are compatible to human health and readily biodegradable created opportunities for vegetable oils for application in paints and printing inks. The formulation of vegetable oil methyl ester based 'green' offset printing ink that reduces the volatile organic compounds (VOC) has been discussed in the present study. Methyl esters of rapeseed, soybean, rice bran and palm oil have been prepared and their physical properties have been measured and compared with standard petroleum feed stock. Varnishes were prepared with these esters and their properties are also compared with that of the petroleum based products. Rheological properties of the inks are also evaluated and compared with standard printing ink using petroleum based solvent. In general performance of the ester-based printing inks are comparable with that of the mineral oil based product. On the basis of tack stability and gloss, ester based inks are much superior than the mineral oil based products. In conclusion, a new non-volatile diluent for printing ink has been developed. The diluent is made from common vegetable oils like rapeseed, soybean, rice bran and palm oil, a renewable source that is environmental friendly. Vegetable oil esters offer a cost effective solution for mineral oil based printing ink to meet VOCs regulations.     

环氧生物质油在合成润滑油基础油的研究进展

衍生于植物油和动物脂肪的生物质油是生物润滑油的重要原料。与矿物油相比,生物质油具有低毒性、高生物降解性、高润滑性和良好的黏温性等优点,但其含双键和甘油酯基导致低温流动性和氧化稳定性差。因此,生物质油不宜直接作为润滑油基础油使用。生物质油经环氧化改性增加了氧化稳定性,加强了对金属表面的吸附,提高了润滑性。但是,单纯进行环氧化改性,也会导致油品的黏温性和低温流动性变差。因此,需要对环氧生物质油进一步开环改性。对比选择性氢化、异构化等改性方法,环氧化-开环方法反应条件温和,分子设计空间大。本文总结了由环氧植物油通过开环醚构化、酰化合成生物基础油的现状和发展趋势, 重点阐述了环氧植物油及其衍生物环氧脂肪酸甲酯与有机醇、羧酸和酸酐合成润滑油的研究进展,分析了改性分子结构对润滑油性能的影响,讨论了合成生物润滑油研究中尚存的问题, 并认为优化改性工艺、开发绿色高效的催化剂是未来的发展方向。     

The Role of Oil Phase in the Stability and Physicochemical Properties of Oil-in-Water Emulsions in the Presence of Gum Tragacanth

Different emulsions based on six types of vegetable oils (sunflower, canola, sesame, olive, coconut, and palm olein) were studied to investigate the role of the oil phase in the stability and physicochemical characteristics of oil-in-water emulsions prepared with gum tragacanth. The results indicated that the stability, rheological parameters, and size distribution of emulsions were dependent on the oil type. Based on the interfacial tension value, the type of oil did not have a significant effect on the gum tragacanth-emulsifying properties. The formulation based on sunflower and coconut oil led to producing more stable emulsion and a sample containing palm olein resulted in an unstable emulsion. Rheological analysis revealed that the sample based on palm olein showed the lowest consistency coefficient (2.10 ± 0.05 Pas ⁿ), elastic modulus (3.90 ± 0.21 Pa), and energy of cohesion (80.87 ± 1.1 J m⁻³). This study revealed that using oils with lower viscosity and higher density led to the higher stability of the emulsion samples.